Anti-block systems (ABS) are known which have a slip control and produce for this purpose a reference value which approximates to the speed of the vehicle, the rise of which reference value is limited so as not to permit physically impossible changes of the vehicle speed to enter into the production of the reference value.
From EP-A2 0299 510 an anti-block system is known in which the vehicle speed is determined extrinsically to the control operation by the speed of the more rapidly rotating, undriven wheel.
In DE-AL 30 11 541 an arrangement for detecting the skidding or sliding of wheels of total adhesion locomotives is described. In this case the revolutions of the driven axles are detected and a pseudo-axle simulated by means of an integrator; the signal of the integrator serves as the reference value.